A quiescent current (IQ) of an integrated circuit (IC) is an operating current required to operate an IC's basic functionality, such as for example, powering an internal precision reference voltage, an oscillator, a thermal shutdown circuit, a state machine or other logic gates. IQ is generally defined as the current drawn by an IC in a no-load and nonswitching but enabled condition. The IQ travels inside the IC to ground. In a no load condition, typically, no current leaves the IC to an output terminal. In a nonswitching condition, typically, no power switch in the IC is on (closed). For some ICs, this means that the IC is in a high-impedance condition with a power stage that is disconnected from the output, except perhaps for certain IC components such as integrated MOSFET body diodes that cannot be turned off. In an enabled condition, typically, the IC is turned on and is not in a shutdown condition.
A voltage divider circuit includes multiple voltage load components, across which voltage drops, which are coupled in series between a first node and a second node. Voltage is measured at junctions between the voltage load components. A bias voltage is applied to the first node. A voltage at each junction is proportional to the voltage drop across the series-connected electrical components disposed between that junction and the second node.
FIG. 1 is an illustrative drawing representing a resistor voltage divider circuit 102 that includes multiple resistors coupled in series. The exampled resistor voltage divider circuit includes resistors R1 to Rk that each acts as a resistor load voltage coupled in series between a first node and a second node. A divider output voltage is provided at a junction between two resistors coupled between the first and second nodes. The first node 104 is coupled to a bias voltage Vout. The second node 106 is coupled to ground. For example, a third node 108 is shown at a junction between resistors Rk-x and Rk-x-1. The divider output voltage at the third node is equals the voltage drop across the k-x-1 resistors coupled between Rk-x and ground divided by a total voltage drop across all k resistors. Typically, a resistor voltage divider in an IC includes diffused resistors coupled in series to provide divided voltage outputs at junctions between the resistors. Unfortunately, such a structure ordinarily requires a relatively surface large area, which is not preferred in an IC.
FIG. 2 is an illustrative drawing representing an active device voltage divider circuit 202 that includes multiple active devices coupled in series. Active voltage divider circuits have been provided that include multiple active field effect transistor (FET) devices Mn1-Mnk, each having its gate coupled to its drain. The multiple FET devices are coupled in series form a chain of FET devices to provide divided voltage outputs at junctions between them. The function of each series-connected FET device is the same as a resistor in a resistor voltage divider although its I-V curve is not linear and typically its area is much less than resistor to realize the same IQ. For example, a divider voltage output voltage at the drain of FET device Mn2 equals the voltage drop across the FET devices coupled between the drain of Mn2 and ground divided by a total voltage drop across all k FET devices. An active device voltage divider typically occupies less IC area to realize a given IQ than would a resistor divider. However, IQ for an active device voltage divider circuit can vary significantly with semiconductor manufacturing process corner changes.